bi300650n_si_001.pdf (8.21 MB)
Identification of Oxidized Amino Acid Residues in the Vicinity of the Mn4CaO5 Cluster of Photosystem II: Implications for the Identification of Oxygen Channels within the Photosystem
journal contribution
posted on 2012-08-14, 00:00 authored by Laurie
K. Frankel, Larry Sallans, Patrick A. Limbach, Terry M. BrickerAs a light-driven water–plastoquinone oxidoreductase,
Photosystem
II produces molecular oxygen as an enzymatic product. Additionally,
under a variety of stress conditions, reactive oxygen species are
produced at or near the active site for oxygen evolution. In this
study, Fourier-transform ion cyclotron resonance mass spectrometry
was used to identify oxidized amino acid residues located in several
core Photosystem II proteins (D1, D2, CP43, and CP47) isolated from
spinach Photosystem II membranes. While the majority of these oxidized
residues (81%) are located on the oxygenated solvent-exposed surface
of the complex, several residues on the CP43 protein (354E, 355T, 356M, and 357R) which are
in close proximity (<15 Å) to the Mn4CaO5 active site are also modified. These residues appear to be associated
with putative oxygen/reactive oxygen species exit channel(s) in the
photosystem. These results are discussed within the context of a number
of computational studies which have identified putative oxygen channels
within the photosystem.